Fluidic flame detector

ABSTRACT

A fluidic flame monitoring device is disclosed, the device comprising a fluidic amplifier, either of the bistable or proportional type, the power stream of which is modulated or switched in accordance with the temperature above an external flame. Connected to a control port of the fluidic amplifier is a chamber coupled to a source of fluidic pressure, the chamber incorporating a vented pressure regulating output. In the preferred inventive embodiment, an elongated thin-walled tube is coupled between the pressure regulating output of the chamber and the atmosphere, the flow resistance of the tube varying in response to the temperature of an external flame applied thereto. In one preferred embodiment, the absence of a flame alters the control signal pressure at the control port of the fluidic amplifier, switching the output power stream thereof. The switching of the output power stream is detected as an indication of flameout. When a proportional amplifier is utilized, modulation of the output power stream occurs in response to variations in flame temperature. The device can be utilized to control and shut off the fuel supply to an external burner in response to flameout.

United States Patent 91 Swartz FLUIDIC FLAME DETECTOR Inventor: Elmer L.Swartz, Annandale, Va.

Assignee: The United States'of America as represented by the Secretaryof the Army, Washington, DC.

Filed: Aug. 14, 1974 App], No; 497,413

References Cited UNITED STATES PATENTS 5/l970 Berrey 73/363 8/1971 Fehret al.. 137/804 11/197 Meyer 137/804 l/l973 Monsen 137/804 X PrimaryExaminer-Edward G. Favors Attorney, Agent, or Firm-Nathan Edelberg;Robert P. Gibson; Saul Elbaum [451 July 22, 1975 s71 ABSTRACT A fluidicflame monitoring device is disclosed, the de ature above an externalflame. Connected to a control port of the fluidic amplifier is a chambercoupled to a source of fluidic pressure, the chamber incorporating avented pressure regulating output. In the preferred inventiveembodiment, an elongated thin-walled tube is coupled between thepressure regulating output of the chamber and the atmosphere, the flowresistance of the tube varying in response to the temperature of anexternal flame applied thereto. In one preferred embodiment, the absenceof a flame alters the control signal pressure at the control port of thefluidic amplifier, switching the output power stream thereof. Theswitching of the output power stream is detected as an indication offlameout. When a proportional amplifier is utilized, modulation of theoutput power stream occurs in response to variations in flametemperature, The device can be utilized to control and shut off the fuelsupply to an external burner in response to flameout.

6 Claims, 1 Drawing Figure FUEL CONTROL VALVE READOUT -36 3s 1 4o (if 234\ BURNER 42 FLAME MONITOR FLUIDIC FLAME DETECTOR RIGHTS OF THEGOVERNMENT The invention described herein may be manufactured, used, andlicensed by or for the United States Government for governmentalpurposes without the payment to me of any royalty thereon.

BACKGROUND OF THE INVENTION This invention generally relates to flamemonitoring devices and is particularly concerned with a flame monitoringdevice manufactured of fluidic components.

For purposes of safety, as well as for other control purposes, it isoften times necessary to monitor the presence or absence of a flame in agiven piece of equipment. For example, and as concerns a heating systemutilizing oil burners, it is necessary to detect the absence of a flameso that the fuel supply to the burner can be rapidly shut off. Anotherenvironment in which flame detectors have found utility is monitoringthe occurrence of a flameout in aircraft engines, so that suitablecorrective measures can be taken. Flame monitoring devices also findutility in fire alarm systems and the like.

Considering the wide-spread utility as just briefly indicated above, theprior art is replete with various apparatus all suitable for detectingthe presence or absence of a flame. Most of such apparatus, however,exhibits one or more disadvantages, disqualifying the ap paratus for usein a particular environment. For example, many flame monitoring devicesare electrical in nature, precluding their safe utilization in anexplosive atmosphere. One specific such electrical device, utilizingthermocouples exhibits an extremely slow response time. Opticalmonitoring devices, on the other hand, necessarily incorporate a viewingarea and it is often times difficult to maintain the viewing area cleanand thus ensure reliability of the device. Mechanical apparatus, on theother hand, typically incorporate many moving parts, decreasing theuseful life of the apparatus and furtherdegrading the response timethereof.

SUMMARY OF THE INVENTION It is thus apparent that a need exists in theflame monitoring art for the provision ofa device of markedly differentconstruction and which serves to overcome the above-noted disadvantagesof the prior-art. It is the primary objective of the instant inventionto provide such a novel flame monitoring device.

A further objective of the instant invention is the provision of a flamemonitoring device which utilizes fluidic components and requiresvirtually no moving parts.

Still another objective of the instant invention is the provision of aflame monitoring device which exhibits a rapid response time and whichcan be utilized in explosive environments with a high degree of safety.

Yet, another objective of the instant invention is the provision of aflame monitoring device which not only has the capability of indicatingthe presence or absence of a flame, but which further can indicate thetemperature of the flame somonitored.

These objectives are implemented by the instant invention which will beseen to comprise a fluidic flame monitoring device utilizing a fluidicamplifier, either of the bistable or proportional type, having an inletchannel, an outlet channel, and a control port communicating with aninteraction region such that a control signal applied to the controlport modulates a power stream flowing between the inlet and outletchannels. Connected to the control port and providing the control signalthereto is the outlet of a chamber or tank which is coupled to aconstant type flow or volume fluid source. The chamber furtherincorporates a vented pressure regulating output and an elongatedthinwalled tube constituting a means for controlling the amount ofventing through the pressure regulating output is connected thereto.When the elongated tube is placed in an external flame, the viscosity ofthe fluid flowing therein would suddenly increase as would the effectivetube flow resistence, thereby reducing the I venting to the atmosphereand causing the pressure within the tank or chamber to increase. Thisincreased pressure which, as aforestated, constitutes the controlsignal, causes the power stream in the outlet channel of the fluidicamplifier to be modulated. A readout mechanism, such as a meter, detectsthe modulation or pressure in the outlet channel and thereby serves toprovide an indication of the presence, or absence, of a flame. In theevent that a proportional amplifier is utilized, the amount ofmodulation, rather than bistable switching, indicates the temperature ofthe external flame.

BRIEF DESCRIPTION OF THE DRAWINGS The invention itself will be betterunderstood and further features and advantages thereof will becomeapparent from the following detailed description of a preferredinventive embodiment, which description makes reference to the appendedsheet of drawing, wherein the single FIGURE thereon represents inschematic illustration one embodiment of the instant invention utilizinga bistable fluidic amplifier for control of the fuel supply to anexternal burner.

DETAILED DESCRIPTION OF THE PREFERRED INVENTIVE EMBODIMENT Withreference now to the drawing, the basic fluidic flame monitoring deviceof the instant invention cornprises a fluidic amplifier means generallydesignated by reference numeral 10 having, in typical fashion, an inletchannel 12, at least one outlet channel, such as channels 14 and 16, atleast one control port, such as control port 18 and 20 communicatingwith an interaction region 22 such that a control signal applied to thecontrol port would serve to modulate a power stream indicated byreference numeral 24 flowing between the inlet and outlet channels.

In the illustrated embodiment, a bistable fluidic amplifier is shownsuch that a change in control signal pressure at control port 20 willserve to switch the power stream from outlet channel 14 to outletchannel 16, and vice versa. As will be appreciated from the discussionherein-below, proportional amplifiers could similarly be utilized toadvantage, the basic requirement being that any such fluidic amplifiershould have a relatively high gain, and have the capability of beingback loaded without deleterious switching effects.

With the embodiment of the invention shown, the fluidic amplifier isnormally biased such that the power stream flows in outlet channel 16 inthe presence of a normal pressure signal at control port 20, the powerstream switching to outlet channel 14 upon an increase in the controlpressure signal. As is also typical, the fluidic amplifier of theinvention includes several atmospheric vents, such as vents 26 and 28ensuring stable operation.

A chamber or tank 30 is provided having an outlet 32 connected to thecontrol port 20 to provide the control signal thereto. A fluid source.such as source 34, is coupled to the chamber or tank 30, source 34preferably being of the variety providing a constant rate of flow, orconstant volume. Chamber or tank 30 further incorporates a ventedpressure regulating output indicated at reference numeral 36. Coupled tothis output is a means generally designated by reference numeral 38which controls the amount of venting therethrough in response to thetemperature of an external flame indicated by reference numeral 40 asemanating from an external oil burner or the like 42. In the preferredinventive embodiment. means 38 constitute a thin-walled sensor tubewhich communicates flow of fluid from the tank or chamber 30 to theoutside atmosphere. With the apparatus as shown, and as will be evident,a portion of the fluid provided by source 34 is vented to the atmospherethrough the sensor tube, and a further portion is provided as thecontrol signal at control port 20. Suitable and obvious pressureadjustments must, of course, be made such that the input flow from thehigh impedance 34 will not create enough pressure under normalconditionswithin the tank or chamber 30 to cause the power stream 24 toswitch from its normal condition wherein it exits outlet channel 16, toits switched condition exiting outlet channel 14 as is shown.

When a flame, such as flame 40, is placed under the sensor tub 38, theviscosity of the fluid flowing therethrough would suddenly increase, andthe effective tube flow resistence would likewise suddenly increase,thereby reducing the flow of fluid to the atmosphere, i.e. reducing theventing, and causing the pressure within the chamber or tank 30 to rise.A slight increase in this pressure would cause the high gain fluidicamplifier to switch such that the power stream exits outlet channel 14as shown. A readout gauge 44, such as a pressure monitoring device, iscoupled to the outlet channel 14 of the fluidic amplifier and, under thecircumstances discussed above, readout gauge 44 will measurepressureonly when a flame is present.

If the flame should suddenly go out, the pressure of fluid within thetank or chamber 30 would quickly return to its normal level and thefluidic amplifier 10 would switch back to its bias or normal side,wherein the power stream exits outlet channel 16. The reaction time ofthe system is fast in that the fluid supply through the tube 38 quicklycools the tube, and further due to the fact that the tube 38 iscontemplated to be constructed having walls as thin as is feasible. Inoperation, response time of the device as illustrated constitutes afraction of a second.

One particular utility of the preferred embodiment of the invention isto control the fuel supply to an external burner such as oil burner 42.In this respect, the outlet channel 14 of the fluidic amplifier 10 wouldbe connected to a pressure actuated flow control valve 46 in a fuelsupply line 48 for the external burner 42. In this fashion, the valve 46would be normally biased in an open condition and, when flame-out of theburner was detected, the sudden drop of pressure at outlet channel 14would cause the valve 46 to quickly shut off, and

thus prevent oil from unsafely accumulating at burner 42.

The basic device of the instant invention can be disposed at a locationremote from the high temperature area of flame 40. In this respect, aconduit need only be coupled between the sensor tube 38 and the outlet36 of the pressure chamber 30 as will be evident.

' For those applications in which temperature monitoring in addition toflameout monitoring is desired, fluidic amplifier 10 would constitute aproportional amplifier as opposed to the bistable device abovediscussed.In this event, a change in the temperature of flame 40 impinging uponsensor tube 38 would effect a proportional change in the amount of powerstream flow through outlet channel 14 in conventional fashion.

From the foregoing description, it should be evident that the objectivesset forth at the outset havebeen successfully achieved. It is to beunderstood that the invention described above constitutes but apreferred embodiment, and that obvious modifications thereto can be madeby a person skilled in the art. ACCORD- INGLY What I claim is:

l. A fluidic flame monitoring device comprising: a fluidic amplifiermeans having an inlet channel, an outlet channel, and a control portcommunicating with an interaction region such that a control signalapplied to said control port modulates a power stream flowing betweensaid inlet and output channels; readout means coupled to said outletchannel for providing an indication of the pressure therein; a chambercoupled to a fluid source and having an output connected to said controlport to provide said control signal thereto, said chamber furtherincorporating a vented pressure regulating output; and means coupled tosaid pressure regulating output for controlling the amount of ventingtherethrough in response to the temperature of an external flame;whereby the pressure within said chamber is varied by said externalflame and the power stream within said fluidic amplifier is therebymodulated and indicated.

2. A device as defined in claim 1, wherein said means for controllingthe venting of said pressure regulating output of said chamber comprisesan elongated tube coupled between said pressure regulating output andthe atmosphere, the flow resistence of said tube varying in response tothe temperature of an external flame applied thereto.

3. A device as defined in claim 2, wherein said source of fluidicpressure for said chamber delivers a constant flow fluidic signal.

4. A device as defined in claim 2, wherein said fluidic amplifier is abistable amplifier, said readout means thereby indicating the presenceor absence of a flame.

5. A device as defined in claim 2, wherein said fluidic amplifier is aproportional amplifier, said readout means thereby indicating thetemperature of the flame.

6. A device as defined in claim 2, further including in combinationtherewith a fuel supply line for an external flame burner, a pressureactuated flow control valve in said supply line, and wherein said outletchannel of said fluidic amplifier is connected to said flow controlvalve to provide the pressure for actuation thereof, whereby said fuelsupply is shut off in the absence of a flame.

1. A fluidic flame monitoring device comprising: a fluidic amplifiermeans having an inlet channel, an outlet channel, and a control portcommunicating with an interaction region such that a control signalapplied to said control port modulates a power stream flowing betweensaid inlet and output channels; readout means coupled to said outletchannel for providing an indication of the pressure therein; a chambercoupled to a fluid source and having an output connected to said controlport to provide said control signal thereto, said chamber furtherincorporating a vented pressure regulating output; and means coupled tosaid pressure regulating output for controlling the amount of ventingtherethrough in response to the temperature of an external flame;whereby the pressure within said chamber is varied by said externalflame and the power stream within said fluidic amplifier is therebymodulated and indicated.
 2. A device as defined in claim 1, wherein saidmeans for controlling the venting of said pressure regulating output ofsaid chamber comprises an elongated tube coupled between said pressureregulating output and the atmosphere, the flow resistence of said tubevarying in response to the temperature of an external flame appliedthereto.
 3. A device as defined in claim 2, wherein said source offluidic pressure for said chamber delivers a constant flow fluidicsignal.
 4. A device as defined in claim 2, wherein said fluidicamplifier is a bistable amplifier, said readout means thereby indicatingthe presence or absence of a flame.
 5. A device as defined in claim 2,wherein said fluidic amplifier is a proportional amplifier, said readoutmeans thereby indicating the temperature of the flame.
 6. A device asdefined in claim 2, further including in combination therewith a fuelsupply line for an external flame burner, a pressure actuated flowcontrol valve in said supply line, and wherein said outlet channel ofsaid fluidic amplifier is connected to said flow control valve toprovide the pressure for actuation thereof, whereby said fuel supply isshut off in the absence of a flame.